Exploration company Meteoric Resources (ASX: MEI) has reported the first drillhole to test a giant induced polarisation (IP) chargeability anomaly at the Juruena copper-gold project within Brazil’s Alta Floresta Belt has reached 841m downhole.
The high-response anomaly was detected during exploration last year and contains an intense core which the company said presents an “obvious drill target” approximately 1.5km long and 800m wide.
Drilling of the anomaly commenced in February and was designed to test the porphyry copper-gold potential at depth.
The first hole progressed through complex, classic porphyry geology including felsic to intermediate porphyry intrusives, dolerites and lamprophyres.
These are believed to be overprinted by an intense phyllic alteration with abundant sulphides including copper sulphides and possible gold mineralised zones.
More significantly, quartz-pyrite-molybdenite and quartz-chalcopyrite-bornite veins were encountered from approximately 700m depth.
Meteoric managing director Andrew Tunks said bornite is significant to the exploration results.
“This type of association is important for [our] understanding of the system,” he said.
“It also serves as an indication of higher temperature mineral assemblies and can be used as a vectoring tool to the magmatic system’s hottest portions.”
Juruena rocks are believed to have undergone intense brittle-ductile deformation resulting in strong phyllic alteration and complex vein arrays.
Mr Tunks said this indicates that drilling may be approaching the main copper-gold porphyry target at the Juruena fault earlier than expected.
The geology expected at target is part of a large breccia pipe with magmatic hydrothermal alteration first investigated by Lago Dourado Minerals, in a shallow IP survey and some diamond and reverse circulation drilling.
In addition, several zones of potassic alteration with pyrite have also been intersected and will be assayed for gold.
Major magmatic system
“We are intersecting the right rocks and alteration styles to indicate we are within a major magmatic system,” Mr Tunks said.
“From around 600m depth, we have been logging quartz molybdenite veins and from 700m we have progressed into a zone with quartz, chalcopyrite bornite veins.
“The hole will continue for approximately another 250m into our main copper-gold porphyry target which is the Juruena fault,” he added.